1. Field of the Invention
The present invention relates to a stage unit having a means for limiting the moving range of a moving table on which a target positioning object is mounted, a drive table driven by a linear motor and capable of easily performing origin detection, and a scanning exposure apparatus for manufacturing semiconductor elements or the like by using the same.
2. Related Background Art
To manufacture semiconductor elements, liquid crystal display elements, or the like by using the photolithography technique, a projection exposure apparatus is conventionally used, in which a pattern formed on a reticle (or a photomask) is exposed, through a projection optical system, onto a wafer (or a glass plate) coated with a photoresist.
In recent years, one chip pattern of a semiconductor element or the like tends to become larger. For this reason, a projection exposure apparatus for exposing a pattern on a reticle, which has a larger size, onto a wafer is required. To meet such a requirement for increasing the exposure area with a so-called step and repeat type projection exposure apparatus for performing full exposure of the entire pattern on the reticle, the projection optical system must be made larger. However, this results in an increase in manufacturing cost of a projection optical system having high imaging performance on the entire surface of the wide exposure field.
Therefore, a so-called step and scan type scanning exposure apparatus has received a great deal of attention. In this apparatus, after each shot area of the wafer is moved to the scan start position, the reticle, which is being illuminated, is scanned in a direction crossing the optical axis of the projection optical system. In synchronism with this scanning, the wafer is scanned in the direction crossing the optical axis of the projection optical system, thereby exposing the pattern of the reticle onto each shot area of the wafer.
According to the present invention, there is provided a stage unit arranged in a scanning exposure apparatus which illuminates a mask on which a transfer pattern is formed, scans the mask in the first direction (Y direction or xe2x88x92Y direction) as a predetermined scanning direction, and synchronously scans a photosensitive substrate in a direction corresponding to the scanning direction, thereby sequentially exposing the pattern of the mask onto the photosensitive substrate, comprising a base, a scanning stage arranged to be freely moved in the first direction on the base, a fine adjustment stage, arranged to be freely moved, with respect to the scanning stage, within predetermined ranges in the first direction of a target scanning object and a second direction perpendicular to the first direction, for mounting the target scanning object thereon, a first electromagnetic actuator for driving the fine fu adjustment stage in the second direction with respect to the scanning stage, and a second electromagnetic actuator for driving the fine adjustment stage in the first direction with respect to the scanning stage with a larger thrust than that of the first electromagnetic actuator.
In this case, as each of the first and second electromagnetic actuators, an electromagnetic actuator of a moving magnet type in which a stationary member having a coil is fixed on the scanning stage side is used. Cooling means for cooling the stationary member of each of the first and second electromagnetic actuators by circulating a predetermined cooling fluid is preferably arranged.
In addition, a movable mirror fixed on the fine adjustment stage, and an interferometer for irradiating a measurement light beam on the movable mirror to detect a displacement of the fine adjustment stage with respect to the scanning stage are provided. The cooling means preferably circulates the cooling fluid from a portion near an optical path of the light beam from the interferometer.
Furthermore, one of the first and second electromagnetic actuators is preferably constituted by a pair of electromagnetic actuators which are parallelly arranged.
In the scanning exposure apparatus, a large a inertial force in the first direction as the scanning direction is applied to the fine adjustment stage particularly at the start and end of scanning.
According to the stage unit of the present invention, however, an actuator having a small thrust is used as the electromagnetic actuator for driving the fine adjustment stage in the second direction (X direction or xe2x88x92X direction) because the inertial force applied to the fine adjustment stage in the second direction which is not the scanning direction can be almost neglected. With this arrangement, the shape and weight of the movable member of the electromagnetic actuator can be reduced. For this reason, the overall weight of the fine adjustment stage is reduced, thereby improving the control performance of the stage. In addition, the capacity of the coil of the electromagnetic actuator in the second direction can also be reduced. Since a heat generation amount from the coil is also decreased, heat deformation of each stage is minimized, thereby minimizing the adverse influence of heat to the measurement equipment for position measurement.
When each of the first and second electromagnetic actuators is an electromagnetic actuator of a moving magnet type, and the cooling means for cooling the stationary member of each of the first and second electromagnetic actuators by circulating the predetermined cooling liquid is arranged, the fine adjustment stage is separated from the coil as a heat source. For this reason, the heat deformation of the fine adjustment stage can be minimized as compared to a case wherein an electromagnetic actuator of a moving coil type is used.
When the stationary member as a heat source is liquid-cooled, the total heat generation amount is minimized. It is mechanically easy to cool the stationary member in this manner.
The movable mirror fixed on the fine adjustment stage, and the interferometer for irradiating the measurement light beam on the movable mirror to detect the displacement of the fine adjustment stage with respect to the scanning stage are arranged, and the cooling fluid is circulated from the portion near the optical path of the light beam from the interferometer. In this case, when the cooling fluid has the largest cooling capability, the electromagnetic actuators are sequentially cooled from the portion near the optical path. For this reason, temperature adjustment of a gas on the optical path is stably performed, thereby maintaining a high measurement precision.
When one of the first and second electromagnetic actuators is constituted by a pair of electromagnetic actuators which are parallelly arranged, driving in the rotational direction is enabled by applying thrusts to the pair of electromagnetic actuators in opposite directions.
According to the present invention, there is provided a stage unit comprising a moving table for mounting a target positioning object thereon, a base for mounting the moving table thereon to be freely moved in a predetermined direction, driving means for driving the moving table in the predetermined direction with respect to the base, switch means for stopping an operation of the driving means when the moving table moves beyond an allowable movement range in the predetermined direction, and push-back means for generating a biasing force for pushing back the moving table to the allowable movement range side before the switch means operates.
In this case, the biasing force of the push-back means is preferably larger than the frictional force between the moving table and the base. At the same time, the biasing force is preferably a force within a range smaller than that of the driving force in the normal operation of the driving means.
An elastic member is used as an example of the push-back means.
A linear motor is used as an example of the driving means.
According to the present invention, when the moving table moves beyond the allowable movement range because of runaway and comes close to the switch means, the push-back means starts to apply the biasing force to the moving table to the allowable movement range side. When the moving table further moves, the switch means operates to stop the operation of the driving means. More specifically, the driving force of the driving means to the moving table is eliminated, and the moving table is stopped.
Even in this state, the push-back means is operating. Since the push-back means has a biasing force larger than the frictional force between the moving table and the base, the moving table is pushed back to the allowable movement range side. The switch means is set in an inoperative state, and driving of the moving table by the driving means is enabled. When, e.g., the control system of the driving means shifts to an error sequence upon operation of the switch means, and the driving means it driven upon completion of error processing, runaway of the moving table to the switch means side is prevented.
When the push-back means has an elastic member such as a coil spring or a rubber member, the biasing force can be generated by the elastic member with a simple arrangement without particularly adding a power source or the like.
When the driving means is constituted by a linear motor, and the switch means operates to stop supplying the driving power to the linear motor, the linear motor has no driving force at all. Therefore, only the frictional force and the biasing force from the push-back means act on the moving table, thereby easily pushing back the moving table to the allowable movement range side.
According to the present invention, there is provided a drive table comprising a driving system for two-dimensionally moving a table along an X direction and a Y direction, which are perpendicular to each other, X position detection means for detecting a position of the table along the X direction, Y position detection means for detecting the position of the table along the Y direction, xcex8 detection means for detecting a rotation amount xcex8 about a xcex8 axis perpendicular to the X and Y directions of the table, X reference position detection means for detecting that a predetermined first position on the table reaches a predetermined X reference position on an X reference coordinate axis, Y reference position detection means for detecting that a predetermined second position on the table reaches a predetermined Y reference position on a Y reference coordinate axis, xcex8 reference position detection means for detecting that a predetermined third position on the table reaches a predetermined xcex8 reference position on another X or Y reference coordinate axis, and a calculation unit for converting detection values from the X position detection means, the Y position detection means, and the xcex8 detection means into coordinate values on an X-Y reference coordinate plane on the basis of detection signals obtained from the X reference position detection means, the Y reference position detection means, and the xcex8 reference position detection means and detection values from the X position detection means, the Y position detection means, and the xcex8 detection means, which are obtained upon generation of the detection signals.
The driving system is preferably a non-contact type driving unit.
It is preferable that the X reference position detection means have an X position detection light-shielding plate arranged at the predetermined first position on the table, and an X reference position detection sensor, arranged at the predetermined X reference position, for generating a signal when the light-shielding plate reaches the X reference position, the Y reference position detection means have a Y position detection light-shielding plate fill arranged at the predetermined second position on the table, and a Y reference position detection sensor, arranged at the predetermined Y reference position, for generating a signal when the light-shielding plate reaches the Y reference position, the xcex8 reference position detection means have a xcex8 position detection light-shielding plate arranged at the predetermined third position on the table, and a xcex8 reference position detection sensor, arranged at the predetermined xcex8 reference position, for generating a signal when the light-shielding plate reaches the xcex8 reference position, and the calculation means include reference rotation amount calculation means for obtaining a reference rotation amount about an axis perpendicular to the X-Y reference coordinate plane of the table from a shift between a detection signals from the xcex8 reference position detection sensor and a detection signal from the X reference position detection means or the Y reference position detection means.
It is preferable that the X reference position detection means have X direction driving means for pressing an X direction side edge of the table against an X reference stopper provided on the reference coordinate axis in advance, and X press detection means for detecting that the X direction side edge is pressed against the X reference stopper, the Y reference position detection means have Y direction driving means for pressing a Y direction side edge of the table against a Y reference stopper provided on the reference coordinate axis in advance, and Y press detection means for detecting that the Y direction side edge is pressed against the Y reference stopper, the xcex8 reference position detection means have xcex8 direction driving means for pressing the X or Y direction side edge of the table against a xcex8 reference stopper provided to be separated from the X or Y reference stopper on the reference coordinate axis by a predetermined distance, and xcex8 press detection means for detecting that the X or Y direction side edge is pressed against the xcex8 reference stopper, and the calculation means include rotation amount reset means for setting a detection value from rotation amount detection means to a reference rotation amount in accordance with a detection signal from the xcex8 press detection means and a detection signal from the X or Y press detection means.
The drive table of the present invention has the reference position detection means for detecting that the predetermined positions on the table reach the predetermined reference positions on the reference coordinate axes for the three displacements, displacements in the X and Y directions of the table, and the rotation amount xcex8 about the xcex8 axis perpendicular to the X and Y directions, and the calculation means for converting the detection values from the position detection means, which are obtained upon generation of the detection signals obtained from the reference position detection means into the coordinate values on the reference coordinates. For this reason, origin detection with respect to the reference coordinate axes of the drive table can be precisely performed.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.